@ehBeth,
I can't help but notice, judging by the names of Canadian hockey players, that a lot of Canadians are of Eastern European descent. Immigrants from Poland and Eastern Europe would clearly cause no problem for most Canadians, instead would be considered the family getting together, so to speak.
Make it a 2-for-1 deal. Canada joins the EU while the UK gets to stay. Works out great for everyone. Canada gets new markets plus a bunch of their cousins from the Old World joining them. Europe gets access to a free market including a lot of Canadian mineral and industrial wealth, and keeps the UK, the world's sixth largest economy.
This is not just a win-win situation. For Canada, the UK, and the EU, it's a win-win-win.